Many industries require packing bulk materials into packages of different sizes to enhance storage, transportation and sales. A typical example of such industries is the food industry which usually sells products, such as candies, frozen foods in pack. In these industries, weighing machines are adapted to provide a weight measurement for packing articles. The weighing machines now in use are automatic apparatus in order to save labor and time consumed in measurement.
One of the common weighing machines now in use comprises a plurality of weighing units (so that it is referred to as multiple weighing apparatus) which measure the weights of separate batches of articles supplied from a supply source. A control device which may be operated by a micro-processor or similar electronic device computes the combination of weight values obtained from the weighing units and selects a best combination therefrom which is equal to or very close to a pre-set reference weight value to discharge the articles contained in the weighing units which together provide the best combination. The discharged articles which have in total a weight very close to a desired value are then packed.
In such an automatic weighing machine, each of the weighing units comprises a weighing hopper for accommodating therein a batch of articles, the weight of which is sensed by the weighing unit and a pool hopper for quickly supplying articles to the weighing hopper. Each of the hoppers is equipped with a gate to be operated by a four-bar linkage which is in turn controlled by the control device to open or close the gate and thus allowing the articles therein to pass therethrough.
An example of the above type automatic weighing machines is disclosed in U.S. Pat. No. 4,545,446, issued to Rihei Kokabu on Oct. 8, 1985. The automatic weighing machine disclosed in this patent, however, possesses several disadvantages. For example, since there is only a single gate controlled by a four-bar linkage, a strong impact occurs between the gate and the hopper body when the gate is closed to the end. Vibration is also easy to induce in such a four-bar design.
It is therefore the purpose of the present invention to provide an automatic multiple weighing machine of such a type, each weighing unit of which has a dual-acting hopper gates controlled by a six-bar linkage, especially a Stephenson III type linkage, so as to overcome the deficiencies of the prior art automatic multiple weighing machines.